Grain free senior cat food? Not sure about my cats diet :(

Hi all!!

I have a sweet 17 year old baby. I found her on the street when she was 9 years old, hiding in my familys gutter. Shes with me at college now as an emotional support cat, and she loves that i work at a pet store :).

Shes been on IAMS senior for most her life with me, and i didnt until a couple years ago learn about the importance of wet food, where id give her one or two a week (what i could afford, she drinks a lot of water luckily). That is grain-in, and shes always been a lb or two overweight, but very energetic. She threw up OFTEN. Like 1-3x a week. Not including hairballs.

Recently, ive been feeding Nulo Senior, but thats grain-free with legumes being VERY high up on the ingredients list. (She also gets different brands of wet food multiple times a week, on nights she doesnt get that, she gets rehydrated Steves Freezedried Whitefish raw food). Shes also been getting a tiny drop of InClover Digestive Aid for the last couple weeks. She hasnt been throwing up at ALL, shes had even more energy, her skin/coat seem happy. She seems happy.

But im still worried. Should i be mixing in a grain in food with the grain free? Would that even rid the risk? Shes 17, i dont want the reason she leaves me to be something i did have control over like DCM. Any advice, info, thoughts, testimonials or anything would be appreciated :)